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post-meta-icon"></i><span class="post-meta-label">Updated</span><time class="post-meta-date-updated" datetime="2023-05-15T01:25:43.172Z" title="Updated 2023-05-15 09:25:43">2023-05-15</time></span><span class="post-meta-categories"><span class="post-meta-separator">|</span><i class="fas fa-inbox fa-fw post-meta-icon"></i><a class="post-meta-categories" href="/bk/categories/%E5%90%8E%E7%AB%AF/">后端</a></span></div><div class="meta-secondline"><span class="post-meta-separator">|</span><span class="post-meta-pv-cv" id="" data-flag-title="【Redis】工具类封装与解决缓存击穿，缓存穿透"><i class="far fa-eye fa-fw post-meta-icon"></i><span class="post-meta-label">Post View:</span><span id="busuanzi_value_page_pv"><i class="fa-solid fa-spinner fa-spin"></i></span></span></div></div></div></header><main class="layout" id="content-inner"><div id="post"><article class="post-content" id="article-container"><h4 id="工具类"><a href="#工具类" class="headerlink" title="工具类"></a>工具类</h4><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span 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class="line">123</span><br><span class="line">124</span><br><span class="line">125</span><br><span class="line">126</span><br><span class="line">127</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@slf4j</span></span><br><span class="line"><span class="meta">@Component</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">CacheClient</span> &#123;</span><br><span class="line">    </span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">final</span> StringRedisTemplate stringRedisTemplate;</span><br><span class="line">    </span><br><span class="line">    <span class="keyword">public</span> <span class="title function_">CacheClient</span><span class="params">(StringRedisTemplate stringRedisTemplate)</span> &#123;</span><br><span class="line">        <span class="built_in">this</span>.stringRedisTemplate = stringRedisTemplate;</span><br><span class="line">    &#125;</span><br><span class="line">    </span><br><span class="line">    <span class="comment">// 创建10个线程的线程池</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">static</span> <span class="keyword">final</span> <span class="type">ExecutorService</span> <span class="variable">CACHE_REBUILD_EXECUTOR</span> <span class="operator">=</span> Executors.newFixedThreadPool( nThreads: <span class="number">10</span>); </span><br><span class="line">    </span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">    * 设置普通的缓存</span></span><br><span class="line"><span class="comment">    */</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">set</span><span class="params">(String key, Object value,Long time, TimeUnit unit)</span> &#123;</span><br><span class="line">       stringRedisTemplate.opsForValue().setIfAbsent(key, value: JSONUtil.toJsonStr(value), timeout: time, unit);</span><br><span class="line">    &#125;</span><br><span class="line">    </span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">    * 设置有逻辑过期的缓存</span></span><br><span class="line"><span class="comment">    */</span></span><br><span class="line">    <span class="keyword">public</span> <span class="keyword">void</span> <span class="title function_">setwithLogicalExpire</span><span class="params">(String key, Object value, Long time, TimeUnit unit)</span>&#123;</span><br><span class="line">     	<span class="comment">// 设置逻辑过期</span></span><br><span class="line">        <span class="type">RedisData</span> <span class="variable">redisata</span> <span class="operator">=</span> <span class="keyword">new</span> <span class="title class_">RedisData</span>();</span><br><span class="line">        redisData.setData(value):</span><br><span class="line">        redisData,setExpireTime(LocalDateTime,now().plusSeconds(unit,toSeconds(time)));</span><br><span class="line">        <span class="comment">// 写入Redis</span></span><br><span class="line">        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value));   </span><br><span class="line">    &#125;</span><br><span class="line">    </span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">    * 基于缓存空对象，解决缓存穿透问题</span></span><br><span class="line"><span class="comment">    */</span></span><br><span class="line">    <span class="keyword">public</span> &lt;R,ID&gt; R <span class="title function_">queryWithPassThrough</span><span class="params">(</span></span><br><span class="line"><span class="params">        String keyPrefix, ID id, Class&lt;R&gt; type, Function&lt;ID,R&gt; dbFallback,Long time, TimeUnit unit</span></span><br><span class="line"><span class="params">    )</span> &#123;</span><br><span class="line">        <span class="type">String</span> <span class="variable">key</span> <span class="operator">=</span> keyPrefix + id;</span><br><span class="line">         <span class="comment">// 从redis查询商铺缓存</span></span><br><span class="line">        <span class="type">String</span> <span class="variable">json</span> <span class="operator">=</span> stringRedisTemplate.opsForValue().get(key);</span><br><span class="line">         <span class="comment">// 判断是否存在</span></span><br><span class="line">        <span class="keyword">if</span> (StrUtil.isNotBlank(json)) &#123;<span class="comment">// json不能为null,不能为“”，不能为空格</span></span><br><span class="line">         <span class="comment">// 存在，直接返回</span></span><br><span class="line">          <span class="type">Shop</span> <span class="variable">shop</span> <span class="operator">=</span> JSONUtil.toBean(shopJson, type);</span><br><span class="line">          <span class="keyword">return</span> shop;   </span><br><span class="line">         &#125;</span><br><span class="line"></span><br><span class="line">        <span class="comment">//不存在，根据id查询数据库</span></span><br><span class="line">        <span class="type">R</span> <span class="variable">r</span> <span class="operator">=</span> dbFallback.apply(id);</span><br><span class="line">        <span class="comment">//不存在，返回错误</span></span><br><span class="line">        <span class="keyword">if</span> (r == <span class="literal">null</span>) &#123;</span><br><span class="line">             <span class="comment">// 将空值写入redis</span></span><br><span class="line">            stringRedisTemplate.opsForValue().set(key, value: <span class="string">&quot;&quot;</span> ,CACHE_NULL_TTL，TimeUnit.MINUTES);<span class="comment">// 返回错误信息</span></span><br><span class="line">            <span class="keyword">return</span> <span class="literal">null</span>;   </span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="comment">//存在，写入redis</span></span><br><span class="line">        <span class="built_in">this</span>.set(key, r, time, unit); </span><br><span class="line">        <span class="keyword">return</span> shop;</span><br><span class="line">   &#125;</span><br><span class="line">    </span><br><span class="line">    </span><br><span class="line">    <span class="comment">/**</span></span><br><span class="line"><span class="comment">    * 基于逻辑过期方式，解决缓存击穿问题</span></span><br><span class="line"><span class="comment">    */</span></span><br><span class="line">    <span class="keyword">public</span> &lt;R,ID&gt; R <span class="title function_">queryWithLogicalExpire</span><span class="params">(</span></span><br><span class="line"><span class="params">    String keyPrefix, ID id, Class&lt;R&gt; type, Function&lt;ID,R&gt; dbFallback,Long time, TimeUnit unit</span></span><br><span class="line"><span class="params">    )</span> &#123;</span><br><span class="line">         <span class="type">String</span> <span class="variable">key</span> <span class="operator">=</span> keyPrefix + id;</span><br><span class="line">        <span class="comment">//从redis查询商铺缓存</span></span><br><span class="line">        <span class="type">String</span> <span class="variable">json</span> <span class="operator">=</span> stringRedisTemplate.opsForValue().get(key);</span><br><span class="line">         <span class="comment">//是否命中</span></span><br><span class="line">        <span class="keyword">if</span> (StrUtil.isBlank(json)) &#123;<span class="comment">//shopJson能为null,不能为“”，能为空格</span></span><br><span class="line">         <span class="comment">//存在，直接返回</span></span><br><span class="line">          <span class="keyword">return</span> <span class="literal">null</span>;   </span><br><span class="line">         &#125;</span><br><span class="line"></span><br><span class="line">        <span class="comment">//命中，判断是否缓存过期，需要将jsn反序列化为对象</span></span><br><span class="line">        <span class="type">RedisData</span> <span class="variable">redisData</span> <span class="operator">=</span> JSONUtil.toBean(json,RedisData);</span><br><span class="line">        <span class="type">R</span> <span class="variable">r</span> <span class="operator">=</span> JSONUtil.toBean((JsonObject)redisData.getData(),type);</span><br><span class="line">        <span class="type">LocalDateTime</span> <span class="variable">expireTime</span> <span class="operator">=</span> data.getExpireTime();</span><br><span class="line"></span><br><span class="line">        <span class="comment">//缓存未过期，直接返回店铺信息</span></span><br><span class="line">        <span class="keyword">if</span>(expireTime.isAfter(LocalDateTime.now()))&#123;</span><br><span class="line">            <span class="keyword">return</span> r; </span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="comment">//过期，尝试获取互斥锁</span></span><br><span class="line">        <span class="comment">//能获取互斥锁,没有资源在占用锁（获取锁,等于1说明没有人占用了）</span></span><br><span class="line">        <span class="type">String</span> <span class="variable">lockKey</span> <span class="operator">=</span> LOCK_SHOP_KEY + id;</span><br><span class="line">        <span class="type">boolean</span> <span class="variable">isLock</span> <span class="operator">=</span> tryLock(lockKey)；</span><br><span class="line">        <span class="keyword">if</span>(isLock))&#123;</span><br><span class="line">             <span class="comment">//成功，开启独立线程，实现缓存重建</span></span><br><span class="line">             CACHE_REBUILD_EXECUTOR.submit(()-&gt;&#123;</span><br><span class="line">                 <span class="keyword">try</span>&#123;</span><br><span class="line">                    <span class="comment">//重建缓存</span></span><br><span class="line">                    <span class="type">R</span> <span class="variable">r</span> <span class="operator">=</span> dbFallback.apply(id);</span><br><span class="line">                    <span class="comment">// 设置延迟为200s,模拟复制业务查询后的key</span></span><br><span class="line">                    Thread.sleep(<span class="number">200</span>); </span><br><span class="line">                    <span class="built_in">this</span>.setwithLogicalExpire(key, r, time, unit);</span><br><span class="line">                 &#125; <span class="keyword">catch</span> (Exception e) &#123;</span><br><span class="line">                    <span class="keyword">throw</span> <span class="keyword">new</span> <span class="title class_">RuntimeException</span>(e) </span><br><span class="line">                 &#125; <span class="keyword">finally</span> &#123;</span><br><span class="line">                    <span class="comment">//释放锁</span></span><br><span class="line">                     unlock(lockKey); </span><br><span class="line">                 &#125;</span><br><span class="line">             &#125;)     </span><br><span class="line">         &#125;</span><br><span class="line"></span><br><span class="line">        <span class="comment">//返回过期数据</span></span><br><span class="line">        <span class="keyword">return</span> r;</span><br><span class="line">	&#125;</span><br><span class="line">    </span><br><span class="line">    </span><br><span class="line">    </span><br><span class="line">    <span class="comment">// 获取锁</span></span><br><span class="line">    <span class="keyword">private</span> <span class="type">boolean</span> <span class="title function_">tryLock</span><span class="params">(String key)</span> [</span><br><span class="line">        <span class="type">Boolean</span> <span class="variable">flag</span> <span class="operator">=</span> stringRedisTemplate.opsForValue().setIfAbsent(key, value: <span class="string">&quot;1&quot;</span>， timeout: <span class="number">10</span>, TimeUnit.SECONDS):</span><br><span class="line">        <span class="keyword">return</span> BooleanUtil.isTrue(flag);</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="comment">// 释放锁</span></span><br><span class="line">    <span class="keyword">private</span> <span class="keyword">void</span> <span class="title function_">unlock</span><span class="params">(String key)</span> &#123;</span><br><span class="line">        stringRedisTemplate.delete(key);</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

<h4 id="测试"><a href="#测试" class="headerlink" title="测试"></a>测试</h4><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Service</span></span><br><span class="line"><span class="keyword">public</span> <span class="keyword">class</span> <span class="title class_">ShopServiceImpl</span> <span class="keyword">extends</span> <span class="title class_">ServiceImpl</span>&lt;ShopMapper, Shop&gt; <span class="keyword">implements</span> <span class="title class_">IShopService</span> &#123;</span><br><span class="line">    <span class="meta">@Resource</span></span><br><span class="line">    <span class="keyword">private</span> StringRedisTemplate stringRedisTemplate:</span><br><span class="line">    <span class="meta">@Resource</span></span><br><span class="line">    <span class="keyword">private</span> CacheClientcacheClient  </span><br><span class="line">        </span><br><span class="line">    <span class="meta">@Override</span></span><br><span class="line">    <span class="keyword">public</span> Result <span class="title function_">queryById</span><span class="params">(Long id)</span> &#123;</span><br><span class="line">        <span class="comment">// 解决缓存穿透</span></span><br><span class="line">        <span class="comment">//写法1</span></span><br><span class="line">        <span class="type">Shop</span> <span class="variable">shop</span> <span class="operator">=</span> cacheclient.queryWithPassThrough(CACHE_SHOPKEY, id, Shop.class, id2 -&gt; getByid(id2), CACHE_SHOP_TTL，TimeUnit.MINUTES );</span><br><span class="line">        <span class="comment">//写法2</span></span><br><span class="line">       <span class="type">Shop</span> <span class="variable">shop</span> <span class="operator">=</span> cacheclient.queryWithPassThrough(CACHE_SHOPKEY, id, Shop.class, <span class="built_in">this</span>::getById, CACHE_SHOP_TTL，TimeUnit.MINUTES );</span><br><span class="line">       </span><br><span class="line">        <span class="comment">// 互斥锁解决缓存击穿</span></span><br><span class="line">        <span class="comment">// Shop shop = queryWithMutex(id);</span></span><br><span class="line">        </span><br><span class="line">        <span class="comment">// 逻辑过期解决缓存击穿</span></span><br><span class="line">        <span class="type">Shop</span> <span class="variable">shop</span> <span class="operator">=</span> cacheclient.queryWithLogicalExpire(CACHE_SHOPKEY,id,Shop.class,<span class="built_in">this</span>::getById,CACHE_SHOP_TTL，TimeUnit.MINUTES);</span><br><span class="line">        <span class="keyword">if</span> (shop == <span class="literal">null</span>) &#123;</span><br><span class="line">            <span class="keyword">return</span> Result.fail(<span class="string">&quot;店铺不存在!&quot;</span>);</span><br><span class="line">        &#125;</span><br><span class="line">        <span class="comment">// 7.返回</span></span><br><span class="line">        <span class="keyword">return</span> Result.ok(shop);          </span><br><span class="line">     &#125;</span><br><span class="line">  </span><br><span class="line">    </span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>



<p>给id为1数据，先缓存预热（再缓存击穿）</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"><span class="meta">@Test</span></span><br><span class="line"><span class="keyword">void</span> <span class="title function_">testSaveShop</span><span class="params">()</span> <span class="keyword">throws</span> InterruptedException &#123;</span><br><span class="line">    <span class="type">Shop</span> <span class="variable">shop</span> <span class="operator">=</span> shopService.getById(<span class="number">1L</span>);</span><br><span class="line">	cacheClient.setWithLogicalExpire( key: CACHE_SHOP_KEY + <span class="number">1L</span>, shop, <span class="number">10L</span>, TimeUnit,SECONDS);</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

</article><div class="post-copyright"><div class="post-copyright__author"><span class="post-copyright-meta">Author: </span><span class="post-copyright-info"><a href="https://gitee.com/CWH6">cwh</a></span></div><div class="post-copyright__type"><span class="post-copyright-meta">Link: </span><span class="post-copyright-info"><a href="https://gitee.com/CWH6/2023/05/03/Redis%E5%B7%A5%E5%85%B7%E7%B1%BB%E5%B0%81%E8%A3%85%E4%B8%8E%E8%A7%A3%E5%86%B3%E7%BC%93%E5%AD%98%E5%87%BB%E7%A9%BF%EF%BC%8C%E7%BC%93%E5%AD%98%E7%A9%BF%E9%80%8F/">https://gitee.com/CWH6/2023/05/03/Redis%E5%B7%A5%E5%85%B7%E7%B1%BB%E5%B0%81%E8%A3%85%E4%B8%8E%E8%A7%A3%E5%86%B3%E7%BC%93%E5%AD%98%E5%87%BB%E7%A9%BF%EF%BC%8C%E7%BC%93%E5%AD%98%E7%A9%BF%E9%80%8F/</a></span></div><div class="post-copyright__notice"><span class="post-copyright-meta">Copyright Notice: </span><span class="post-copyright-info">All articles in this blog are licensed under <a target="_blank" rel="noopener" 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